docker: ca-certificates should not be removed. (#3868)

.travis.yml

@@ -31,7 +31,7 @@ script:
 
 # push image
 - >
-  if [ "$TRAVIS_BRANCH" == "master" ] && [ "$TRAVIS_PULL_REQUEST" == "false" ]; then
+  if [ "$TRAVIS_BRANCH" == "master" ] && [ "$TRAVIS_PULL_REQUEST" == "false" ] && [ "$ARCH" == "x86_64" ]; then
     docker login -u="$DOCKER_USER" -p="$DOCKER_PASS"
     docker push minio/minio:edge-armhf
   fi

Dockerfile

@@ -7,7 +7,8 @@ ENV CGO_ENABLED 0
 WORKDIR /go/src/github.com/minio/
 
 RUN  \
-     apk add --no-cache --virtual .build-deps git go musl-dev ca-certificates && \
+     apk add --no-cache ca-certificates && \
+     apk add --no-cache --virtual .build-deps git go musl-dev && \
      go get -v -d github.com/minio/minio && \
      cd /go/src/github.com/minio/minio && \
      go install -v -ldflags "$(go run buildscripts/gen-ldflags.go)" && \

Dockerfile.armhf

@@ -7,7 +7,8 @@ ENV CGO_ENABLED 0
 WORKDIR /go/src/github.com/minio/
 
 RUN  \
-     apk add --no-cache --virtual .build-deps git go musl-dev ca-certificates && \
+     apk add --no-cache ca-certificates && \
+     apk add --no-cache --virtual .build-deps git go musl-dev && \
      go get -v -d github.com/minio/minio && \
      cd /go/src/github.com/minio/minio && \
      go install -v -ldflags "$(go run buildscripts/gen-ldflags.go)" && \